Air conditioner

ABSTRACT

An air conditioner includes a compressing element, a refrigerant cooler, an expansion element, a refrigerant heater, a magnetic field generating part, a circulation volume rate ascertaining part and a control unit. The magnetic field generating part generates a magnetic field in order to perform inductive heating. The circulation volume rate ascertaining part ascertains a circulating refrigerant volume rate. The control unit performs magnetic field output control when the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part has increased. When this control is performed the magnetic field generating part is caused to generate a magnetic field, the magnetic field generated by the magnetic field generating part is increased, or the upper limit of the strength of the magnetic field generated by the magnetic field generating part is increased.

TECHNICAL FIELD

The present invention relates to an air conditioner.

BACKGROUND ART

In the conventional art, an air conditioner that comprises a refrigerant heating apparatus that employs electromagnetic induction heating has been proposed.

For example, Patent Document 1 (i.e., Japanese Unexamined Patent Application Publication No. 2007-255736) below proposes an air conditioner that, in order to efficiently heat a refrigerant by induction heating, controls the start of induction heating in a state wherein the volume rate of circulation of the refrigerant has been secured to some degree.

SUMMARY OF THE INVENTION Technical Problem

In the art disclosed in Patent Document 1 (i.e., Japanese Unexamined Patent Application Publication No. 2007-255736) discussed above, the volume rate of circulation secured is determined with a view toward efficient heating of the refrigerant; however, the refrigerant is not directly induction heated but rather is heated by the transmission of heat from a heat generating member, such as a magnetic body, that is itself heated by induction heating. Consequently, even if a certain volume rate of circulation can be secured to some degree, the volume rate of circulation needed to perform induction heating sometimes cannot be secured.

The present invention was conceived in consideration of the point discussed above, and an object of the present invention is to provide an air conditioner that is capable of hindering a member, which generates heat by induction heating, from generating heat excessively.

Solution to Problem

An air conditioner according to a first aspect of the present invention, which comprises at least a compressing mechanism, a refrigerant cooler, an expansion mechanism, and a refrigerant heater, further comprises a magnetic field generating part, a circulation volume rate ascertaining part, and a control unit. The magnetic field generating part generates a magnetic field in order to inductively heat at least one element selected from the group consisting of a refrigerant piping, which is for circulating a refrigerant to the compressing mechanism, the refrigerant cooler, the expansion mechanism, and the refrigerant heater; and a member that thermally contacts the refrigerant flowing through the refrigerant piping. The circulation volume rate ascertaining part ascertains a circulating refrigerant volume rate of a refrigeration cycle that comprises at least the compressing mechanism, the refrigerant cooler, the expansion mechanism, and the refrigerant heater. The control unit performs magnetic field output control that, when the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part has increased, performs at least one process selected from the group consisting of causing the magnetic field generating part to generate a magnetic field, increasing the magnetic field generated by the magnetic field generating part, and raising the upper limit of the strength of the magnetic field generated by the magnetic field generating part.

In this air conditioner, when the volume rate at which the refrigerant is suctioned by the compressing mechanism is low, there is a risk that, should the magnitude of the magnetic field generated by the magnetic field generating part increase and thereby increase the degree of the induction heating, the portion to be inductively heated will generate heat excessively.

On the other hand, in this air conditioner, it is possible to inhibit the induction heated portion from being heated excessively because the magnetic field is regulated by, for example, generating the magnetic field if the volume rate at which the refrigerant is circulating has increased, increasing the strength of the generated magnetic field, and the like.

An air conditioner according to a second aspect of the present invention is the air conditioner according to the first aspect of the present invention, wherein the magnetic field generating part generates a magnetic field in order to inductively heat at least one element selected from the group consisting of the suction refrigerant piping, which is the refrigerant piping on a suction side of the compressing mechanism, and the member that thermally contacts the refrigerant flowing through the suction refrigerant piping.

In this air conditioner, the refrigerant that is about to be suctioned by the compressing mechanism is rapidly heated and the refrigerant flowing through the refrigerant piping that is significantly spaced apart from the compressing mechanism is not rapidly heated. Furthermore, refrigerant flowing on the suction side of the compressing mechanism either has a high degree of dryness or is in a superheated state and therefore tends to rise in temperature because its sensible heat tends to change more than would be the case wherein the latent heat of the refrigerant in the vapor-liquid two-phase state and the like and flowing more on the upstream side changes.

On the other hand, in this air conditioner, because magnetic field output control is performed after the volume rate at which the refrigerant is circulating has increased, it is possible to prevent excessive induction heating in the state wherein the volume rate at which the refrigerant is circulating is low. Thereby, even if the refrigerant that passes on the suction side of the compressing mechanism and that tends to rise in temperature is thereby heated, it is possible to inhibit the excessive heating of the induction heated portion.

An air conditioner according to a third aspect of the present invention is the air conditioner according to the first aspect or the second aspect of the present invention, wherein the circulation volume rate ascertaining part makes its determination based on at least a prescribed piston displacement volume of the compressing mechanism, a drive frequency of the compressing mechanism, and the density of the refrigerant suctioned by the compressing mechanism.

In this air conditioner, it is possible to perform magnetic field output control in accordance with the state of the refrigerant that passes on the suction side of the compressing mechanism.

An air conditioner according to a fourth aspect of the present invention is the air conditioner according to the third aspect of the present invention, further comprising a low pressure ascertaining part and a suctioned refrigerant temperature ascertaining part. The low pressure ascertaining part ascertains the pressure of the refrigerant flowing through a low pressure portion of the refrigeration cycle. The suctioned refrigerant temperature ascertaining part ascertains the temperature of the refrigerant suctioned by the compressing mechanism. The circulation volume rate ascertaining part derives the density of the refrigerant suctioned by the compressing mechanism based on the pressure ascertained by the low pressure ascertaining part and the temperature ascertained by the suctioned refrigerant temperature ascertaining part.

In this air conditioner, the volume rate at which the refrigerant is circulating can be ascertained more accurately.

An air conditioner according to a fifth aspect of the present invention is the air conditioner according to the fourth aspect of the present invention, wherein the suctioned refrigerant temperature ascertaining part is on the suction side of the compressing mechanism in the refrigeration cycle and detects a state quantity of the refrigerant that passes on the downstream side of a portion inductively heated by the magnetic field generating part.

In this air conditioner, it is possible to ascertain a value that is not affected by induction heating by ascertaining a state quantity of the refrigerant that flows on the upstream side of the portion that generates heat by induction heating.

An air conditioner according to a sixth aspect of the present invention is the air conditioner according to the fourth aspect or the fifth aspect of the present invention, wherein the control unit performs the magnetic field output control in any one case selected from the group consisting of the case wherein the suctioned refrigerant of the compressing mechanism is in a moist state and the case wherein the suctioned refrigerant of the compressing mechanism is in a superheated state wherein the degree of superheating is less than a prescribed degree of superheating.

In this air conditioner, if the degree of superheating of the refrigerant suctioned by the compressing mechanism is high, then there is a risk that the rise in the temperature of the portion that generates heat by induction heating will become significant.

On the other hand, in this air conditioner, induction heating is performed if and only if the superheated state wherein the degree of superheating is less than the prescribed degree of superheating obtains or if the moist state obtains. Consequently, even if the drive frequency of the compressing mechanism has been high and the speed at which the refrigerant is flowing has been quick, magnetic field output control is not performed unless either the superheated state wherein the degree of superheating is less than the prescribed degree of superheating obtains or the moist state obtains, which makes it possible to better inhibit excessive superheating.

An air conditioner according to a seventh aspect of the present invention is the air conditioner according to any one aspect of the first through sixth aspects of the present invention, wherein the control unit performs the magnetic field output control if the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part exceeds a prescribed value.

In this air conditioner, even if magnetic field output control is performed and the induction heated portion is caused to generate heat in the state wherein the volume rate at which the refrigerant is circulating exceeds the prescribed value, the large amount of the refrigerant that passes through the surrounding portion inhibits heat generation. Thereby, it is possible to reliably inhibit the excessive generation of heat of the induction heated portion.

Advantageous Effects of Invention

In the air conditioner of the first aspect of the invention, it is possible to inhibit the excessive heating of the induction heated portion.

In the air conditioner of the second aspect of the invention, it is possible to inhibit the excessive heating of the induction heated portion even if the refrigerant that passes on the suction side of the compressing mechanism and that tends to rise in temperature is heated.

In the air conditioner of the third aspect of the invention, it is possible to perform magnetic field output control in accordance with the state of the refrigerant that passes on the suction side of the compressing mechanism.

In the air conditioner of the fourth aspect of the invention, it is possible to more accurately ascertain the refrigerant circulation volume rate.

In the air conditioner of the fifth aspect of the invention, it is possible to ascertain a value that is not affected by induction heating.

In the air conditioner of the sixth aspect of the invention, it is possible to better inhibit excessive superheating.

In the air conditioner of the seventh aspect of the invention, it is possible to reliably inhibit the excessive generation of heat of the induction heated portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram of an air conditioner according to one embodiment of the present invention.

FIG. 2 is an external oblique view of an electromagnetic induction heating unit.

FIG. 3 is an external oblique view that shows the state wherein a shielding cover has been removed from the electromagnetic induction heating unit.

FIG. 4 is an external oblique view of an electromagnetic induction thermistor.

FIG. 5 is an external oblique view of a fuse.

FIG. 6 is a schematic cross sectional view that shows the state wherein the electromagnetic induction thermistor and the fuse are mounted.

FIG. 7 is a cross sectional view of the electromagnetic induction heating unit.

FIG. 8 is a flow chart of moisture protection induction heating control.

FIG. 9 is a flow chart of abnormal superheating inhibition control.

FIG. 10 is an explanatory diagram of the refrigerant piping according to another embodiment (H).

FIG. 11 is an explanatory diagram of the refrigerant piping according to another embodiment (I).

FIG. 12 is a view that shows an example of the layout of ferrite cases according to another embodiment (J).

DESCRIPTION OF EMBODIMENTS

An exemplary case of an air conditioner 1, which comprises an electromagnetic induction heating unit 6 according to one embodiment of the present invention, will now be explained, referencing the drawings.

First Embodiment <1-1> Air Conditioner 1

FIG. 1 is a refrigerant circuit diagram that shows a refrigerant circuit 10 of the air conditioner 1.

The air conditioner 1 is an apparatus wherein an outdoor unit 2, which serves as a heat source side apparatus, and an indoor unit 4, which serves as a utilization side apparatus, are connected by a refrigerant piping, and the space wherein the utilization side apparatus is disposed is air conditioned; furthermore, the air conditioner 1 comprises a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, a motor operated expansion valve 24, an accumulator 25, outdoor fans 26, an indoor heat exchanger 41, an indoor fan 42, a hot gas bypass valve 27, a capillary tube 28, the electromagnetic induction heating unit 6, and the like.

The compressor 21, the four-way switching valve 22, the outdoor heat exchanger 23, the motor operated expansion valve 24, the accumulator 25, the outdoor fans 26, the hot gas bypass valve 27, the capillary tube 28, and the electromagnetic induction heating unit 6 are housed inside the outdoor unit 2. The indoor heat exchanger 41 and the indoor fan 42 are housed inside the indoor unit 4.

The refrigerant circuit 10 comprises a discharge pipe A, an indoor side gas pipe B, an indoor side liquid pipe C, an outdoor side liquid pipe D, an outdoor side gas pipe E, an accumulator pipe F, a suction pipe G, and a hot gas bypass circuit H. A large amount of the refrigerant in the gas state passes through the indoor side gas pipe B and the outdoor side gas pipe E, but the refrigerant passing through these pipes is not limited to the gas state. A large amount of the refrigerant in the liquid state passes through the indoor side liquid pipe C and the outdoor side liquid pipe D, but the refrigerant passing through these pipes is not limited to the liquid state.

The discharge pipe A connects the compressor 21 and the four-way switching valve 22. A discharge temperature sensor 29 d, which detects the temperature of the refrigerant passing through the discharge pipe A, is provided to the discharge pipe A. Furthermore, an electric current supply part 21 e supplies an electric current to the compressor 21. The amount of electric power supplied by the electric current supply part 21 e is detected by a compressor electric power detection unit 29 f. Furthermore, a rotational speed ascertaining part 29 r detects the drive rotational speed of a piston of the compressor 21. The indoor side gas pipe B connects the four-way switching valve 22 and the indoor heat exchanger 41. A first pressure sensor 29 a, which detects the pressure of the refrigerant passing through the indoor side gas pipe B, is provided along the indoor side gas pipe B. The indoor side liquid pipe C connects the indoor heat exchanger 41 and the motor operated expansion valve 24. The outdoor side liquid pipe D connects the motor operated expansion valve 24 and the outdoor heat exchanger 23. The outdoor side gas pipe E connects the outdoor heat exchanger 23 and the four-way switching valve 22. A second pressure sensor 29 g, which detects the pressure of the refrigerant passing through the outdoor side gas pipe E, is provided along the outdoor side gas pipe E.

The accumulator pipe F connects the four-way switching valve 22 and the accumulator 25 and, in the state wherein the accumulator 25 is installed in the outdoor unit 2, extends in the vertical directions. The electromagnetic induction heating unit 6 is mounted to part of the accumulator pipe F. At least a heat generating portion of the accumulator pipe F, which is enveloped by a coil 68 (discussed below), comprises a magnetic pipe F2 provided such that it envelops a copper pipe F1 wherein the refrigerant flows. The magnetic pipe F2 is made of steel use stainless (SUS) 430. SUS 430 is a ferromagnetic material; when placed in a magnetic field, eddy currents are induced, which generate heat by the action of Joule heat induced by the material's own electrical resistance. The portion of the piping that constitutes the refrigerant circuit 10 and that is outside of the magnetic pipe F2 comprises copper pipes. By performing electromagnetic induction heating in this manner, the accumulator pipe F can generate heat by electromagnetic induction, and thereby the refrigerant that is suctioned into the compressor 21 via the accumulator 25 can be heated. Thereby, the heating capacity of the air conditioner 1 can be improved. In addition, for example, even if the compressor 21 is not sufficiently heated when heating operation is started up, the electromagnetic induction heating unit 6 can perform rapid heating, thereby supplementing the capacity shortfall during startup. Furthermore, if the four-way switching valve 22 switches to the cooling operation state and the defrosting operation, which eliminates frost that adheres to the outdoor heat exchanger 23 and the like, is performed, then the compressor 21 can compress the rapidly heated refrigerant by virtue of the electromagnetic induction heating unit 6 rapidly heating the accumulator pipe F. Consequently, the temperature of the hot gas discharged from the compressor 21 can be rapidly raised. Thereby, the time needed by the defrosting operation to thaw the frost can be shortened. Thereby, even if it is necessary to perform the defrosting operation when appropriate during heating operation, it is possible to return to the heating operation as quickly as possible and thereby to improve user comfort.

Furthermore, a suction temperature sensor 19 that detects the temperature of the refrigerant that flows between the electromagnetic induction heating unit 6 and the four-way switching valve 22 is provided to the accumulator pipe F. In the state wherein a refrigeration cycle performs heating operation, the suction temperature sensor 19 detects the temperature of the refrigerant flowing on the downstream side of the electromagnetic induction heating unit 6 before the refrigerant is heated by induction heating by the electromagnetic induction heating unit 6.

The suction pipe G connects the accumulator 25 and the suction side of the compressor 21.

The hot gas bypass circuit H connects a branching point A1, which is provided along the discharge pipe A, and a branching point D1, which is provided along the outdoor side liquid pipe D. The hot gas bypass valve 27, which is capable of switching between the state in which the refrigerant is permitted to pass through the hot gas bypass circuit H and the state in which it isn't, is disposed along the hot gas bypass circuit H. Furthermore, the capillary tube 28, which lowers the pressure of the refrigerant passing through the hot gas bypass circuit H, is provided along the hot gas bypass circuit H between the hot gas bypass valve 27 and the branching point D1. Because the pressure of the refrigerant can approach that of the refrigerant after the pressure has been decreased by the motor operated expansion valve 24 during heating operation, the capillary tube 28 can hinder a rise in the pressure of the refrigerant in the outdoor side liquid pipe D by supplying hot gas, which has passed through the hot gas bypass circuit H, to the outdoor side liquid pipe D.

The four-way switching valve 22 is capable of switching between a cooling operation cycle and a heating operation cycle. In FIG. 1, solid lines indicate the connection state wherein heating operation is performed, and dotted lines indicate the connection state wherein cooling operation is performed. During heating operation, the indoor heat exchanger 41 functions as a cooler of the refrigerant, and the outdoor heat exchanger 23 functions as a heater of the refrigerant. During cooling operation, the outdoor heat exchanger 23 functions as a cooler of the refrigerant, and the indoor heat exchanger 41 functions as a heater of the refrigerant.

One end of the outdoor heat exchanger 23 is connected to the end part of the outdoor side gas pipe E on the outdoor heat exchanger 23 side, and the other end of the outdoor heat exchanger 23 is connected to the end part of the outdoor side liquid pipe D on the outdoor heat exchanger 23 side. In addition, an outdoor heat exchanger temperature sensor 29 c, which detects the temperature of the refrigerant flowing through the air conditioner 1, is provided to the outdoor heat exchanger 23. Furthermore, an outdoor temperature sensor 29 b, which detects the outdoor air temperature, is provided to the outdoor heat exchanger 23 on the downstream side in the direction of the airflow.

An indoor temperature sensor 43, which detects the indoor temperature, is provided inside the indoor unit 4. In addition, an indoor heat exchanger temperature sensor 44, which detects the temperature of the refrigerant on the indoor side liquid pipe C, along which the motor operated expansion valve 24 is connected, is provided in the indoor heat exchanger 41.

A control unit 11 is constituted by the connection of an outdoor control unit 12, which controls equipment disposed inside the outdoor unit 2, and an indoor control unit 13, which controls equipment disposed inside the indoor unit 4, via a communications wire 11 a. The control unit 11 performs various control functions with respect to the air conditioner 1.

In addition, a timer 95, which counts in order to measure the time elapsed when various control functions are performed, is provided to the outdoor control unit 12.

Furthermore, a controller 90, which accepts the input of settings from the user, is connected to the control unit 11.

<1-2> Electromagnetic Induction Heating Unit 6

FIG. 2 is a schematic oblique view of the electromagnetic induction heating unit 6 mounted to the accumulator pipe F. FIG. 3 is an external oblique view that shows the state wherein a shielding cover 75 has been removed from the electromagnetic induction heating unit 6. FIG. 4 is an external oblique view of an electromagnetic induction thermistor 14. FIG. 5 is an external oblique view of a fuse 15. FIG. 6 is a cross sectional view for the state wherein the electromagnetic induction thermistor 14 and the fuse 15 are mounted to the accumulator pipe F. FIG. 7 is a cross sectional view of the electromagnetic induction heating unit 6 mounted to the accumulator pipe F.

The electromagnetic induction heating unit 6 is disposed such that it covers the magnetic pipe F2, which is the heat generating portion of the accumulator pipe F, from the outer side in the radial directions and causes the magnetic pipe F2 to generate heat by electromagnetic induction heating. The heat generating portion of the accumulator pipe F has a double pipe structure that comprises the copper pipe F1 on the inner side and the magnetic pipe F2 on the outer side.

The electromagnetic induction heating unit 6 comprises a first hex nut 61, a second hex nut 66, a first bobbin cover 63, a second bobbin cover 64, a bobbin main body 65, a first ferrite case 71, a second ferrite case 72, a third ferrite case 73, a fourth ferrite case 74, first ferrite parts 98, second ferrite parts 99, the coil 68, the shielding cover 75, the electromagnetic induction thermistor 14, the fuse 15, and the like.

The first hex nut 61 and the second hex nut 66 are made of resin, and the electromagnetic induction heating unit 6 and the accumulator pipe F are stably fixed using a C ring (not shown). The first bobbin cover 63 and the second bobbin cover 64 are made of resin and cover the accumulator pipe F from the outer side in the radial directions at the upper end position and the lower end position, respectively. The first bobbin cover 63 and the second bobbin cover 64 each have four screw holes, which are for screwing the first through fourth ferrite cases 71-74 (discussed below) to the first bobbin cover 63 and the second bobbin cover 64 using screws 69. Furthermore, the second bobbin cover 64 has an electromagnetic induction thermistor insertion opening 64 f, which is for inserting the electromagnetic induction thermistor 14 into the second bobbin cover 64 in order to mount the electromagnetic induction thermistor 14 to the outer surface of the magnetic pipe F2. In addition, the second bobbin cover 64 has a fuse insertion opening 64 e, which is for inserting the fuse 15 into the second bobbin cover 64 in order to mount the fuse 15 to the outer surface of the magnetic pipe F2. As shown in FIG. 4, the electromagnetic induction thermistor 14 comprises an electromagnetic induction thermistor detecting part 14 a, an outer side projection 14 b, a side surface projection 14 c, and an electromagnetic induction thermistor wiring 14 d, which converts the detection result of the electromagnetic induction thermistor detecting part 14 a to a signal and transmits such to the control unit 11. The electromagnetic induction thermistor detecting part 14 a has a shape that conforms to the curved shape of the outer surface of the accumulator pipe F and has a substantial contact surface area. As shown in FIG. 5, the fuse 15 comprises a fuse detection part 15 a, an asymmetrically shaped member 15 b, and a fuse wiring 15 d, which converts the detection result of the fuse detection part 15 a to a signal and transmits such to the control unit 11. If the control unit 11 receives a notification from the fuse 15 that the temperature detected exceeds a prescribed limit, then the control unit 11 performs control such that the supply of electric power to the coil 68 is stopped, thereby avoiding thermal damage to the equipment. The bobbin main body 65 is made of resin, and the coil 68 is wound around the bobbin main body 65. The coil 68 is wound helically around the outer side of the bobbin main body 65, the directions in which the accumulator pipe F extends being the axial directions. The coil 68 is connected to a control printed circuit board (not shown), and receives the supply of a high frequency electric current. The output of the control printed circuit board is controlled by the control unit 11. As shown in FIG. 6, the electromagnetic induction thermistor 14 and the fuse 15 are mounted in the state wherein the bobbin main body 65 and the second bobbin cover 64 are mated. Here, in the state wherein the electromagnetic induction thermistor 14 is mounted, satisfactory pressure contact between the electromagnetic induction thermistor 14 and the outer surface of the magnetic pipe F2 is maintained by a leaf spring 16, which presses the electromagnetic induction thermistor 14 inward in the radial directions of the magnetic pipe F2. In addition, in the state wherein the fuse 15 is mounted, too, satisfactory contact pressure between the fuse 15 and the outer surface of the magnetic pipe F2 is likewise maintained by a leaf spring 17, which presses the fuse 15 inward in the radial directions of the magnetic pipe F2. Thus, because tight contact is satisfactorily maintained between the electromagnetic induction thermistor 14 and the outer surface of the accumulator pipe F as well as between the fuse 15 and the outer surface of the accumulator pipe F, responsiveness is improved and sudden changes in temperature owing to electromagnetic induction heating can be detected rapidly. The first ferrite case 71 is inserted into the first bobbin cover 63 and the second bobbin cover 64 from the directions in which the accumulator pipe F extends and is fixed by the screws 69. The first ferrite case 71 through the fourth ferrite case 74 each house the first ferrite parts 98 and the second ferrite parts 99, which are made of ferrite—a raw material that has high magnetic permeability. As shown in the cross sectional view of the accumulator pipe F and the electromagnetic induction heating unit 6 of FIG. 7, by capturing the magnetic field generated by the coil 68 and thereby forming a path for the magnetic flux, the first ferrite parts 98 and the second ferrite parts 99 tend not to externally leak the magnetic field. The shielding cover 75 is disposed at the outermost circumferential portion of the electromagnetic induction heating unit 6 and collects the magnetic flux that cannot be completely gathered by the first ferrite parts 98 and the second ferrite parts 99 alone. Thereby, virtually none of the magnetic flux leaks to the outer side of the shielding cover 75; furthermore, the location at which the magnetic flux is generated can be determined independently.

<1-3> Electromagnetic Induction Heating Control

Control is performed wherein the electromagnetic induction heating unit 6 discussed above causes the magnetic pipe F2 of the accumulator pipe F to generate heat at startup, namely, to start heating operation when the refrigeration cycle is caused to perform heating operation, when heating performance is supplemented, and when defrosting operation is performed.

Here, as an example of the various types of control performed by the electromagnetic induction heating unit 6 when supplementing heating performance, control for inhibiting an abnormal rise in the temperature of the magnetic pipe F2 of the accumulator pipe F will be explained.

(Abnormal Superheating Inhibition Control)

Abnormal superheating inhibition control is control performed after control at startup of the compressor 21 and the like has ended in order to verify—in the regular control state wherein the state of the distribution of the refrigerant in the refrigerant circuit 10 of the air conditioner 1 has stabilized—that the volume rate at which the refrigerant is circulating through the accumulator pipe F is sufficiently secured when the electromagnetic induction heating unit 6 starts induction heating for the purpose of, for example, supplementing heating operation capacity.

Here, the control unit 11 calculates the volume rate at which the refrigerant is circulating in the refrigeration cycle (i.e., the volume rate at which the refrigerant passes through the magnetic pipe F2 portion of the accumulator pipe F) by multiplying the piston displacement volume of the compressor 21, which is stored in memory (not shown) as a predetermined quantity, the drive rotational speed of the compressor 21, which is ascertained by the rotational speed ascertaining part 29 r, and the density of the refrigerant suctioned into the compressor 21. The suctioned refrigerant density is calculated by the control unit 11 based on the refrigerant pressure detected by the second pressure sensor 29 g and the refrigerant temperature detected by the suction temperature sensor 19.

In the regular control state, which is the state that obtains after the various types of control performed at the startup of the air conditioner 1 have ended, the control unit 11—in the state wherein the drive frequency of the compressor 21 is maintained at the rated maximum frequency—performs control that responds to changes such as a change in the outdoor air temperature and a change in the user setting temperature by a variation in the circulating refrigerant volume rate owing to regulation of the degree of opening of the motor operated expansion valve 24. Here, the control unit 11 controls the degree of opening of the motor operated expansion valve 24 such that the degree of supercooling of the refrigerant that passes between the indoor heat exchanger 41 and the motor operated expansion valve 24 in the heating operation state, is maintained at 5° C. This degree of supercooling is obtained by virtue of the control unit 11 calculating the difference between the saturation temperature corresponding to the pressure detected by the second pressure sensor 29 g and the temperature detected by the indoor heat exchanger temperature sensor 44.

The explanation below references the flow chart of moisture abnormal superheating inhibition control shown in FIG. 8.

In a step S11, the control unit 11 determines whether the regular control state obtains. Here, if it is determined that the regular control state does obtain, then the method transitions to a step S12. Furthermore, in the regular control state, the output of the electromagnetic induction heating unit 6 is zero.

In the step S12, the control unit 11 determines whether the volume rate at which the refrigerant is circulating in the refrigeration cycle is greater than or equal to a prescribed abnormal superheating inhibition volume rate. If it is less than the abnormal superheating inhibition volume rate, then the method repeats the step S12. If it is greater than or equal to the abnormal superheating inhibition volume rate, then the method transitions to a step S13.

In the step S13, the control unit 11 causes the electromagnetic induction heating unit 6 to start induction heating the accumulator pipe F.

In a step S14, the control unit 11 waits for the elapse of a prescribed time while maintaining the control state as is.

In a step S15, the control unit 11 once again determines whether the volume rate at which the refrigerant is circulating in the refrigeration cycle is greater than or equal to the prescribed abnormal superheating inhibition volume rate. If it is greater than or equal to the abnormal superheating inhibition volume rate, then the method returns to the step S14. If it is less than the abnormal superheating inhibition volume rate, then the method transitions to a step S16.

In the step S16, the control unit 11 causes the electromagnetic induction heating unit 6 to stop induction heating the accumulator pipe F.

In so doing, it is possible to prevent an abnormal rise in the temperature of the accumulator pipe F by ensuring the fluidity of the refrigerant in the accumulator pipe F when the electromagnetic induction heating unit 6 performs induction heating.

<Characteristics of the Air Conditioner 1 of the First Embodiment>

In the air conditioner 1, abnormal superheating inhibition control is performed, before the accumulator pipe F is induction heated by the electromagnetic induction heating unit 6, in order to first verify whether the state that obtains is the state wherein the volume rate at which refrigerant is circulating in the refrigeration cycle is greater than or equal to the abnormal superheating inhibition volume rate. Consequently, the electromagnetic induction heating unit 6 induction heats only in the state wherein the refrigerant is flowing in the refrigeration cycle at a volume rate that is greater than or equal to the abnormal superheating inhibition volume rate and not in the state wherein that volume rate is less than the abnormal superheating inhibition volume rate.

Consequently, the heat supplied to the accumulator pipe F by virtue of the induction heating by the electromagnetic induction heating unit 6 is robbed by the circulating refrigerant, and therefore an abnormal rise in the temperature of the accumulator pipe F can be prevented because a sufficient refrigerant circulation volume rate has been secured.

Second Embodiment

The configuration of an air conditioner of a second embodiment is the same as that of the air conditioner 1 of the first embodiment discussed above, and consequently an explanation thereof is omitted.

In the air conditioner of the second embodiment, abnormal superheating inhibition moisture protection control is performed instead of the abnormal superheating inhibition control of the first embodiment.

Abnormal superheating inhibition moisture protection control is control that is performed after control at the startup of the compressor 21 and the like has ended in order to verify—when the electromagnetic induction heating unit 6 induction heats to supplement heating capacity—that a sufficient volume rate of refrigerant circulating through the accumulator pipe F is secured when the electromagnetic induction heating unit 6 starts induction heating such that liquid compression does not occur in the compressor 21. Here, when the electromagnetic induction heating unit 6 induction heats to supplement heating capacity, the electric power supplied to the coil 68 is set to 50% of the maximum output.

In the state wherein the electromagnetic induction heating unit 6 induction heats to supplement heating capacity, which is the state that obtains after the various types of control performed at the startup of the air conditioner 1 have ended, the control unit 11—in the state wherein the drive frequency of the compressor 21 is maintained at the rated maximum frequency—responds to state changes such as a change in the outdoor air temperature, a change in the set temperature made by the user, and the like by a variation in the circulating refrigerant volume rate owing to regulation of the degree of opening of the motor operated expansion valve 24. Here, the control unit 11 controls the degree of opening of the motor operated expansion valve 24 such that the degree of supercooling of the refrigerant that passes between the indoor heat exchanger 41 and motor operated expansion valve 24 in the heating operation state, is maintained at 5° C. This degree of supercooling is obtained by virtue of the control unit 11 calculating the difference between the saturation temperature that corresponds to the pressure detected by the second pressure sensor 29 g and the temperature detected by the indoor heat exchanger temperature sensor 44.

The control unit 11 calculates the degree of dryness or the degree of superheating of the refrigerant suctioned by the compressor 21 based on the difference between the saturation temperature that corresponds to the pressure detected by the second pressure sensor 29 g and the temperature detected by the electromagnetic induction thermistor 14.

The control unit 11 calculates the degree of dryness or the degree of superheating of the refrigerant discharged by the compressor 21 based on the difference between the saturation temperature that corresponds to the pressure detected by the first pressure sensor 29 a and the temperature detected by the discharge temperature sensor 29 d.

The explanation below references the flow chart of abnormal superheating inhibition moisture protection control shown in FIG. 9.

In a step S21, the control unit 11 determines whether the electromagnetic induction heating unit 6 is induction heating. Here, if it is determined that induction heating is in progress, then the method transitions to a step S22. If induction heating is not in progress, then the method repeats the step S21.

In the step S22, the control unit 11 determines whether an induction heating start condition, wherein the degree of superheating of the suctioned refrigerant is less than 4° C. and the degree of superheating of the discharged refrigerant is less than 10° C., is satisfied. If the induction heating start condition is not satisfied, then the method repeats the step S22. If the induction heating start condition is satisfied, then the method transitions to a step S23.

In the step S23, the control unit 11 determines whether the volume rate at which the refrigerant is circulating in the refrigeration cycle is greater than or equal to a prescribed abnormal superheating inhibition volume rate at maximum output. If less than the abnormal superheating inhibition volume rate at maximum output, then the method repeats the step S23. If greater than or equal to the abnormal superheating inhibition volume rate at maximum output, then the method transitions to a step S24.

In the step S24, the control unit 11 increases the degree to which the electromagnetic induction heating unit 6 induction heats the accumulator pipe F. Namely, the amount of electric power supplied to the coil 68 of the electromagnetic induction heating unit 6 is increased. Here, the electric power supplied to the coil 68 is increased from the state wherein it is at 50% of the maximum output to the state wherein it is at the maximum output.

In the step S25, the control unit 11 waits for the prescribed time to elapse while maintaining the control state as is.

In a step S26, the control unit 11 once again determines whether the volume rate at which the refrigerant is circulating in the refrigeration cycle is greater than or equal to the prescribed abnormal superheating inhibition volume rate at maximum output. If greater than or equal to the abnormal superheating inhibition volume rate at maximum output, then the method transitions to a step S27. If less than the abnormal superheating inhibition volume rate at maximum output, then the method transitions to a step S28.

In the step S27, the control unit 11 determines whether an induction heating end condition, wherein the degree of superheating of the suctioned refrigerant is greater than or equal to 5° C. or the degree of superheating of the discharged refrigerant is greater than or equal to 12° C., is satisfied. If the induction heating end condition is not satisfied, then the method returns to the step S25. If the induction heating end condition is satisfied, then the method transitions to the step S28.

In the step S28, the control unit 11 decreases the output of the electromagnetic induction heating unit 6 in its induction heating of the accumulator pipe F to 50% of the maximum output, which is the state wherein heating performance is supplemented.

In so doing, even if the output of induction heating by the electromagnetic induction heating unit 6 increases, then it is possible to prevent an abnormal rise in the temperature of the accumulator pipe F while preventing liquid compression in the compressor 21 by ensuring the fluidity of the refrigerant of the accumulator pipe F.

<Characteristics of the Air Conditioner 1 of the Second Embodiment>

In the abnormal superheating inhibition moisture protection control of the second embodiment, it is possible to achieve not only the characteristics of the abovementioned first embodiment but also to prevent both liquid compression in the compressor 21 and an abnormal rise in the temperature of the accumulator pipe F.

Furthermore, if, in the second embodiment, the output of the electromagnetic induction heating unit 6 is further increased while the electromagnetic induction heating unit 6 is induction heating at an output of 50% in order to supplement heating performance, then it is difficult to determine whether the volume rate at which the refrigerant is circulating through the portion to be induction heated by the electromagnetic induction heating unit 6 has been secured because the temperature detected by the electromagnetic induction thermistor 14 has already risen. In contrast, in the air conditioner 1 of the second embodiment, the suction temperature sensor 19 is installed at a position on the downstream side of the portion to be induction heated by the electromagnetic induction heating unit 6. Consequently, with regard to the volume rate at which the refrigerant is circulating in the refrigeration cycle, it is possible to ascertain the volume rate at which the refrigerant is flowing on the downstream side of the portion to be induction heated by the electromagnetic induction heating unit 6 by deriving the density of that refrigerant, not the volume rate at which the refrigerant is flowing between the induction heating target portion and the compressor 21 in the state after the refrigerant has been heated. Furthermore, if this circulation volume rate is the abnormal superheating inhibition volume rate at maximum output, then the control unit 11 permits the output of the electromagnetic induction heating unit 6 to be set at the maximum. Thereby, even if the electromagnetic induction heating unit 6 performs induction heating at maximum output, it is possible to inhibit an abnormal rise in the temperature of the portion to be induction heated.

Other Embodiments

The above text explained an embodiment of the present invention based on the drawings, but the specific constitution is not limited to these embodiments, and it is understood that variations and modifications may be effected without departing from the spirit and scope of the invention.

(A)

The abovementioned embodiment explained an exemplary case wherein SUS 430 is used as the material of the magnetic pipe F2.

However, the present invention is not limited thereto. For example, it can be a conductor such as iron, copper, aluminum, chrome, nickel, and the like, or an alloy containing at least two metals selected from that group.

In addition, the magnetic material may be, for example, one of two types, namely, ferritic or martensitic, or a combination thereof, but is preferably a material that is ferromagnetic and that has a comparatively high electrical resistance and a Curie temperature higher than that of the working temperature range.

Furthermore, the accumulator pipe F herein requires a larger amount of electric power; however, instead of a magnetic body and a material that contains a magnetic body, it may contain a material that can be induction heated.

Furthermore, for example, the magnetic material may constitute all of the accumulator pipe F, only an inner side surface of the accumulator pipe F, or be simply included in the material that constitutes the piping of the accumulator pipe F.

(B)

The abovementioned second embodiment explained an exemplary case wherein the degree of dryness or the degree of superheating of the refrigerant suctioned by the compressor 21 is ascertained based on the temperature detected by the electromagnetic induction thermistor 14.

However, the present invention is not limited thereto.

For example, in the electromagnetic induction thermistor 14, it is difficult to detect the temperature of the refrigerant flowing through the portion to be induction heated while the electromagnetic induction heating unit 6 is induction heating, and therefore a higher temperature is sometimes inadvertently detected owing to the heat generated at the magnetic pipe F2.

In such a case, instead of the electromagnetic induction thermistor 14, a sensor that detects the temperature of the accumulator pipe F at a location spaced apart from the portion to be induction heated to the extent that any error in the transmission of heat by induction heating can be ignored may be further provided between the suction side of the compressor 21 and the portion to be induction heated. Thereby, even while induction heating is in progress, the degree of dryness or the degree of superheating of the refrigerant suctioned by the compressor 21 can be ascertained more accurately.

(C)

The induction heating start condition and the induction heating end condition of the first embodiment and the induction heating start condition and the induction heating end condition of the second embodiment were explained according to exemplary cases wherein the same conditions were set.

However, the present invention is not limited thereto. For example, abnormal superheating inhibition moisture protection control in the second embodiment is control wherein the output of the electromagnetic induction heating unit 6 in performing induction heating is already at 50% and is then further increased to the maximum output. Consequently, the induction heating start condition for increasing the output to the maximum output (i.e., the induction heating start condition in the second embodiment) may be set to a condition wherein the refrigerant suctioned by the compressor 21 is in a moister state than it is in the induction heating start condition of the first embodiment.

(D)

The second embodiment explained an exemplary case wherein, when the circulating refrigerant volume rate is greater than or equal to the abnormal superheating inhibition volume rate at maximum output, the output of the electromagnetic induction heating unit 6 is increased from 50% to the maximum output.

However, the present invention is not limited thereto. For example, the output of the electromagnetic induction heating unit 6 may be adjusted in accordance with the derived circulating refrigerant volume rate.

(E)

The first and second embodiments explained exemplary cases that determine whether the abnormal superheating inhibition volume rate has been reached or whether the abnormal superheating inhibition volume rate at maximum output has been reached.

However, the present invention is not limited thereto. For example, if the output of the electromagnetic induction heating unit 6 cannot be increased because the abnormal superheating inhibition volume rate, the abnormal superheating inhibition volume rate at maximum output, or the like could not be achieved, then control that raises the rotational frequency of the compressor 21 may be performed and a state may be created wherein the capacity of induction heating by the electromagnetic induction heating unit 6 can be actively increased without an attendant abnormal rise in the temperature of the portion to be induction heated.

(F)

In the abovementioned first embodiment, an exemplary case was explained wherein the state of the refrigerant in the refrigeration cycle is stabilized by supercooling degree constant control.

However, the present invention is not limited thereto.

For example, control may be performed wherein the degree of change in the distribution state of the refrigerant in the refrigeration cycle is maintained in a prescribed distribution state or within a prescribed distribution range during a prescribed time. With regard to detecting the distribution state of the refrigerant, for example, a sight glass and the like may be provided in advance to a condenser of the refrigeration cycle and the distribution state of the refrigerant may be ascertained by using the sight glass to ascertain the liquid level of the refrigerant; furthermore, control may be performed to stabilize the distribution state such that it is in the prescribed distribution state or within the prescribed distribution range.

(G)

The abovementioned embodiments explained a case wherein the electromagnetic induction heating unit 6 is mounted to the accumulator pipe F of the refrigerant circuit 10.

However, the present invention is not limited thereto.

For example, the electromagnetic induction heating may be mounted to a refrigerant piping other than the accumulator pipe F. In such a case, a magnetic body, for example, the magnetic pipe F2 is provided to a portion of the refrigerant piping whereto the electromagnetic induction heating unit 6 is provided.

(H)

The abovementioned embodiments explained an exemplary case wherein the accumulator pipe F is configured as a double pipe, namely, as the copper pipe F1 and the magnetic pipe F2.

However, the present invention is not limited thereto.

As shown in FIG. 10, for example, a magnetic body member F2 a and two stoppers F1 a, F1 b may be disposed inside the accumulator pipe F, the refrigerant piping to be heated, or the like. Here, the magnetic body member F2 a contains a magnetic material and generates heat by the electromagnetic induction heating of the abovementioned embodiment. At two locations on the inner side of the copper pipe F1, the stoppers F1 a, F1 b continuously permit the passage of the refrigerant but do not permit the passage of the magnetic body member F2 a. Thereby, the magnetic body member F2 a does not move even when the refrigerant flows. Consequently, the target heating position of the accumulator pipe F and the like can be heated. Furthermore, the heat transfer efficiency can be improved because the magnetic body member F2 a, which generates heat, and the refrigerant directly contact one another.

(I)

Instead of using the stoppers F1 a, F1 b the position of the magnetic body member F2 a explained in the abovementioned other embodiment (H) may be prescribed with respect to the piping.

As shown in FIG. 11, for example, bent portions FW may be provided to the copper pipe F1 at two locations, and the magnetic body member F2 a may be disposed on the inner side of the copper pipe F1 between the two bent portions FW. In so doing, too, the movement of the magnetic body member F2 a can be hindered while the refrigerant is made to pass through.

(J)

The abovementioned embodiment explained a case wherein the coil 68 is helically wound around the accumulator pipe F.

However, the present invention is not limited thereto.

For example, as shown in FIG. 12, coils 168, which are wound around bobbin main bodies 165, are disposed at the circumference of—without being wound around—the accumulator pipe F. Here, each of the bobbin main bodies 165 is disposed such that its axial directions are substantially perpendicular to the axial directions of the accumulator pipe F. In addition, the two pairs, each pair comprising one of the bobbin main bodies 165 and one of the coils 168, are disposed such that they sandwich the accumulator pipe F. In this case, as shown in FIG. 12, a first bobbin cover 163 and a second bobbin cover 164, wherethrough the accumulator pipe F is inserted, are preferably disposed in a state wherein they are mated to the bobbin main bodies 165. In addition, as shown in FIG. 12, the first bobbin cover 163 and the second bobbin cover 164 are preferably interposed by a first ferrite case 171 and a second ferrite case 172, and thereby fixed.

FIG. 12 shows an exemplary case wherein the two ferrite cases 171, 172 are provided such that they sandwich the accumulator pipe F; however, as in the above-mentioned embodiments, ferrite cases may be disposed in four directions around the accumulator pipe F. In addition, as in the abovementioned embodiments, the ferrite parts may be housed therein.

<Miscellaneous>

The above text explained embodiments of the present invention with some examples, but the present invention is not limited to these embodiments. For example, the present invention also includes other combination embodiments obtained by appropriately combining parts of the abovementioned embodiments within a range that a person skilled in the art could effect based on the scope of the invention described above.

INDUSTRIAL APPLICABILITY

The present invention is capable of hindering a member, which generates heat by induction heating, from generating heat excessively, and consequently is particularly useful in an air conditioner that is capable of heating a refrigerant by electromagnetic induction heating.

REFERENCE SIGNS LIST

-   1 Air conditioner -   11 Control unit -   19 Suction temperature sensor (suctioned refrigerant temperature     ascertaining part) -   21 Compressor (compressing mechanism) -   23 Outdoor heat exchanger (refrigerant heater) -   24 Motor operated expansion valve (expansion mechanism) -   29 a First pressure sensor -   29 g Second pressure sensor (low pressure ascertaining part) -   29 r Rotational speed ascertaining part (circulation volume rate     ascertaining part) -   41 Indoor heat exchanger (refrigerant cooler) -   44 Indoor heat exchanger temperature sensor (supercooling degree     ascertaining part) -   68 Coil (magnetic field generating part) -   F Accumulator pipe (suction refrigerant piping)

CITATION LIST Patent Literature Patent Document 1

-   Japanese Unexamined Patent Application Publication No. 2007-255736 

1. An air conditioner comprising: a compressing element; a refrigerant cooler; an expansion element; a refrigerant heater; a magnetic field generating part arranged to generate a magnetic field in order to inductively heat at least one element selected from the group consisting of a refrigerant piping arranged to circulate a refrigerant to the compressing element. the refrigerant cooler, the expansion element, and the refrigerant heater, and a member that thermally contacts the refrigerant flowing through the refrigerant piping; a circulation volume rate ascertaining part arranged and configured to ascertain a circulating refrigerant volume rate of a refrigeration cycle that includes at least the compressing element, the refrigerant cooler, the expansion element, and the refrigerant heater; and a control unit configured to perform a magnetic field output control in which at least one process selected from the group consisting of causing the magnetic field generating part to generate a magnetic field, increasing the magnetic field generated by the magnetic field generating part, and raising the upper limit of the strength of the magnetic field generated by the magnetic field generating part is performed when the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part has increased.
 2. An air conditioner according to claim 1, wherein the magnetic field generating part is further arranged to generate a magnetic field in order to inductively heat at least one element selected from the group consisting of suction refrigerant piping disposed on a suction side of the compressing element, and the member that thermally contacts the refrigerant flowing through the refrigerant piping, the refrigerant flowing through the suction refrigerant piping.
 3. An air conditioner according to claim 1, wherein the circulation volume rate ascertaining part is arranged and configured to ascertain the circulating refrigerant volume rate based on at least a prescribed piston displacement volume of the compressing element, a drive frequency of the compressing element, and density of refrigerant suctioned by the compressing element.
 4. An air conditioner according to claim 3, further comprising: a low pressure ascertaining part arranged and configured to ascertain pressure of the refrigerant flowing through a low pressure portion of the refrigeration cycle; and a suctioned refrigerant temperature ascertaining part is arranged and configured to ascertain temperature of the refrigerant suctioned by the compressing element, the circulation volume rate ascertaining part being is arranged and configured to derive the density of the refrigerant suctioned by the compressing element based on the pressure ascertained by the low pressure ascertaining part and the temperature ascertained by the suctioned refrigerant temperature ascertaining part.
 5. An air conditioner according to claim 4, wherein the suctioned refrigerant temperature ascertaining part is disposed on a suction side of the compressing element in the refrigeration cycle and is further arranged and configured to detect a state quantity of the refrigerant that passes on a downstream side of a portion inductively heated by the magnetic field generating part.
 6. An air conditioner according to claim 4, wherein the control unit is further configured to perform the magnetic field output control in any one case selected from the group consisting of a case when the suctioned refrigerant of the compressing element is in a moist state and a case when the suctioned refrigerant of the compressing element is in a superheated state wherein the degree of superheating is less than a prescribed degree of superheating.
 7. An air conditioner according to claim 1, wherein the control unit is further configured to perform the magnetic field output control if the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part exceeds a prescribed value.
 8. An air conditioner according to claim 5, wherein the control unit is further configured to perform the magnetic field output control in any one case selected from the group consisting of a case when the suctioned refrigerant of the compressing element is in a moist state and a case when the suctioned refrigerant of the compressing element is in a superheated state wherein the degree of superheating is less than a prescribed degree of superheating.
 9. An air conditioner according to claim 6, wherein the control unit is further configured to perform the magnetic field output control if the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part exceeds a prescribed value.
 10. An air conditioner according to claim 2, wherein the circulation volume rate ascertaining part is arranged and configured to ascertain the circulating refrigerant volume rate based on at least a prescribed piston displacement volume of the compressing element, a drive frequency of the compressing element, and density of refrigerant suctioned by the compressing element.
 11. An air conditioner according to claim 10, further comprising: a low pressure ascertaining part arranged and configured to ascertain pressure of the refrigerant flowing through a low pressure portion of the refrigeration cycle; and a suctioned refrigerant temperature ascertaining part is arranged and configured to ascertain temperature of the refrigerant suctioned by the compressing element, the circulation volume rate ascertaining part being is arranged and configured to derive the density of the refrigerant suctioned by the compressing element based on the pressure ascertained by the low pressure ascertaining part and the temperature ascertained by the suctioned refrigerant temperature ascertaining part.
 12. An air conditioner according to claim 11, wherein the suctioned refrigerant temperature ascertaining part is disposed on the suction side of the compressing element in the refrigeration cycle and is further arranged and configured to detect a state quantity of the refrigerant that passes on a downstream side of a portion inductively heated by the magnetic field generating part.
 13. An air conditioner according to claim 11, wherein the control unit is further configured to perform the magnetic field output control in any one case selected from the group consisting of a case when the suctioned refrigerant of the compressing element is in a moist state and a case when the suctioned refrigerant of the compressing element is in a superheated state wherein the degree of superheating is less than a prescribed degree of superheating.
 14. An air conditioner according to claim 2, wherein the control unit is further configured to perform the magnetic field output control if the circulating refrigerant volume rate ascertained by the circulation volume rate ascertaining part exceeds a prescribed value. 